Vehicle steering system

ABSTRACT

An apparatus has a chassis that has a pair of rear wheels that passively rotate and a pair of front wheel sets. Each pair of front wheel sets has an upright with an affixed motor. A front wheel is fixed relative to the upright and engages with the motor. A linkage connects the chassis to each of the uprights and is configured to move the uprights in a first range of motion. A linkage actuator actuates the linkage.

INTRODUCTION

Toy vehicles, such as remote-controlled cars, trucks, and the like, may be used for racing or general entertainment purposes. These toy vehicles may mimic basic driving functionality and performance of large-scale vehicles, but typically cannot perform more advanced driving maneuvers such as circular spins (so called “doughnuts”), or j-shaped turns (commonly referred to as “drifts”). Such maneuvers typically require high-powered, rear wheel drive systems that cannot be incorporated into a toy.

SUMMARY

In one aspect, the technology relates to an apparatus having: a chassis; a pair of rear wheels passively rotatably coupled to the chassis; a pair of front wheel sets, wherein each pair of front wheel sets include: an upright; a motor fixed to the upright; and a front wheel fixed relative to the upright and engaged with the motor; a linkage coupling the chassis to each of the uprights of the pair of front wheel sets, wherein the linkage is configured to move the uprights in a first range of motion; and a linkage actuator for actuating the linkage. In an example, the apparatus further includes a controller fixed to the chassis for sending control signals to the motors and the linkage actuator. In another example, the apparatus further includes a pair of trailing link actuators, and wherein each front wheel set includes a trailing link connecting the upright to one of the pair of trailing link actuators. In yet another example, the trailing link is configured to allow movement of the upright in a second range of motion different than the first range of motion. In still another example, the first range of motion and the second range of motion are substantially orthogonal.

In another example of the above aspect, the linkage includes Ackermann steering geometry. In an example, the controller is configured to send a motor signal to at least one of the motors so as to at least one of (1) rotate the front wheels at different rotational speeds, and (2) rotate the front wheels in different rotational directions. In another example, the controller is configured to send an actuator signal to at least one of the trailing link actuators so as to actuate at least one of the trailing links. In yet another example, each of the pair of rear wheels has a coefficient of friction less than a coefficient of friction of each of the pair of front wheels. In still another example, the pair of rear wheels is coupled to by an axle that is configured to pivot relative to the chassis.

In another aspect, the technology relates to a method of moving a vehicle along a ground surface in a general direction of a curve, wherein the curve includes a curve radius and a center point, and wherein the vehicle includes a plurality of driven front wheels and a plurality of passive rear wheels, and wherein the plurality of driven front wheels include an inside front wheel disposed proximate to the center point and an outside front wheel disposed distal from the center point, the method including: moving the vehicle in a default direction of travel by applying a first force from a ground-engaging surface of at least one of the plurality of driven front wheels to the ground surface; turning a leading surface of the plurality of driven front wheels in a wheel direction away from a general direction of the curve; and applying a second force from the ground-engaging surface of at least one of the plurality of driven front wheels to the ground surface, so as to move the vehicle in the general direction of the curve. In an example, applying the second force includes accelerating a rotational speed of the outside wheel to an accelerated rotational speed greater than a default rotational speed applied to the outside wheel during the default moving operation. In another example, applying the second force includes decelerating a rotational speed of the inside wheel to a decelerated rotational speed less than a default rotational speed applied to the inside wheel during the default moving operation. In yet another example, applying the second force includes reversing a direction of rotation of the inside wheel to a reversed rotational direction opposite a default rotational direction applied to the inside wheel during the default moving operation. In still another example, applying the second force includes changing a center of gravity of the vehicle. In another example, changing the center of gravity of the vehicle includes elevating at least a portion of the vehicle proximate the outside wheel to a raised elevation higher than a default elevation of the portion of the vehicle during the default moving operation.

In another aspect, the technology relates to a method of controlling a vehicle, the method including: sending a default signal to a vehicle control module, wherein the vehicle control module controls at least one of a rotational speed of a wheel, a rotational direction of the wheel, a center of gravity of the vehicle, and an elevation of a portion of the vehicle; receiving a desired direction signal from a vehicle driving controller, wherein the desired direction signal is associated with a desired direction of a turn of the vehicle; based at least in part on the desired direction signal, sending a linkage direction signal to the control module so as to change a directional position of the wheel, wherein the changed directional position of the wheel is in a direction generally opposite the desired direction of the turn of the vehicle; and based at least in part on the desired direction signal, sending a command signal to the control module so as to turn the vehicle generally in the desired direction. In an example, the command signal increases the rotational speed of the wheel to a command signal speed greater than a default speed associated with the default signal. In another example, the command signal decreases the rotational speed of the wheel to a command signal speed less than a default speed associated with the default signal. In yet another example, the command signal reverses the rotational direction of the wheel to a command signal rotational direction opposite a default rotation associated with the default signal. In still another example, the command signal changes a center of gravity of the vehicle to a command signal center of gravity different than a default center of gravity associated with the default signal. In another example, the command signal changes the elevation of the portion of the vehicle to a command signal elevation different than a default elevation associated with the default signal.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a perspective view of a toy vehicle.

FIG. 2A depicts a perspective view of the toy vehicle of FIG. 1, with the body removed.

FIG. 2B depicts a front view of the toy vehicle of FIG. 1, with the body removed.

FIG. 2C depicts a top view of the toy vehicle of FIG. 1, with the body removed.

FIG. 2D depicts a left side view of the toy vehicle of FIG. 1, with the body removed.

FIG. 2E depicts a bottom view of the toy vehicle of FIG. 1, with the body removed.

FIG. 2F depicts a rear view of the toy vehicle of FIG. 1, with the body removed.

FIGS. 3A and 3B depict top and side views, respectively, of a driven wheel for a toy vehicle.

FIGS. 4A and 4B depict schematic top and rear views, respectively, of a vehicle moving in a default direction.

FIGS. 5A and 5B depict schematic top and rear views, respectively, of the vehicle of FIGS. 4A and 4B performing a standard turn.

FIGS. 6A and 6B depict schematic top and rear views, respectively, of the vehicle of FIGS. 4A and 4B performing a drift turn to the right.

FIGS. 7A and 7B depict schematic top and rear views, respectively, of the vehicle of FIGS. 4A and 4B performing a drift turn to the left.

FIG. 8 depicts a method of moving a vehicle.

FIG. 9 depicts a method of controlling a vehicle.

DETAILED DESCRIPTION

FIG. 1 depicts a perspective view of a toy vehicle 100 that includes a housing or body 102, and a plurality of wheels. Two motor-driven front wheels 202 control speed and direction of the vehicle 100, while two passive rear wheels 204 support a rear portion of the vehicle 100. In general, the front wheels 202 display a higher coefficient of friction that the rear wheels 204, for reasons described in more detail below. The front wheels 202 may be made of thermoplastic polyurethane (TPU) which displays a high coefficient of friction. The rear wheels 204 may be made from ABS or similar hard elastomers displaying a high durometer and low coefficient of friction.

A controller 104 may be centrally-located on the chassis 200, and may include a control module that sends control signals to various motors or actuators (as described below) as required or desired for operation of the vehicle 100. Wiring may connect the controller and/or control module to the various motors and actuators. The controller 104 may also operate lights, audio speakers, display screens, or other elements located in or on the body 102. The controller 104 may include or be connected to a Bluetooth or other wireless receiver, which may receive signals from an associated remote driving controller 106, such as a hand-held device, app-enabled smartphone, etc., to allow a user to control the vehicle 100.

FIGS. 2A-2F depict various views of the toy vehicle 100 of FIG. 1, with the body removed. These figures are described concurrently, and not all components are depicted in every one of FIGS. 2A-2F. The various components are supported on a chassis 200. The two front wheels 202 a, 202 b are each connected to dedicated motors 206 a, 206 b, via an enclosed gear set 208 a, 208 b. An upright 210 a, 210 b supports each motor 206 a, 206 b and connects to a linkage 212 that includes tie rods and other components that may be actuated by a linkage actuator 213 disposed on the chassis 200. Together, the wheels, motors, gear sets, and uprights form discrete wheel sets 209 a, 209 b that may function and actuate independently to control the performance of the vehicle 100. In examples, the linkage 212 may be configured with Ackermann steering geometry, although other linkage configurations may also be utilized. Actuation of the linkage actuator 213 moves the linkage 212 so as to articulate the uprights 210 a, 210 b, thus pivoting the wheel sets 209 a, 209 b through a first range of motion R₁ (e.g., from an extreme left position to an extreme right position).

A trailing link 214 a, 214 b in the form of a C-arm connects each upright 210 a, 210 b to an associated trailing link actuator 216 a, 216 b disposed on the chassis 200. The connection may be made, for example, via a connecting rod 218 a, 218 b. Each associated trailing link actuator 216 a, 216 b may apply a force to the connecting rod 218 a, 218 b to lift and lower the connecting rod 218 a, 218 b. Since each trailing link actuator 216 a, 216 b is fixed to the chassis 200, this application of force moves the associated wheel set 209 a, 209 b relative to the chassis 200 in a second range of motion R₂ (e.g., up and down substantially orthogonal to the first range of motion R₁). Since the wheels 202 a, 202 b of each wheel set 209 a, 209 b are in contact with a ground surface, this movement effectively lifts and lowers a portion of the chassis 200 proximate the associated wheel set 209 a, 209 b. The effect of this action is described in more detail below.

The passive (e.g., non-driven) rear wheels 204 a, 204 b are connected to the chassis 200 via an articulating axle 220. The articulating axle 220 connects to the chassis 200 via a pivoting interface 222, which enables the rear wheels 204 a, 204 b to pivot P relative to the chassis 200. This pivoting P action keeps the rear wheels 204 a, 204 b in contact with the ground surface when one of the trailing link actuators 216 a, 216 b lifts an associated part of the chassis 200, as described above. Because the entire chassis 200 moves relative to the front wheels 202 a, 202 b, the articulating axle 220 keeps the rear wheels 204 a, 204 b in contact with the ground surface.

FIGS. 3A and 3B depict schematic top and side views, respectively, of a driven wheel 300 for a toy vehicle V. FIGS. 3A and 3B are used to depict various surfaces and relationships as relevant for describing operation of a vehicle V incorporating the technologies described herein. While both FIGS. 3A and 3B are described concurrently, the ground surface G is depicted only in FIG. 3B. The wheel 300 generally includes a rim 302 and a tire 304 having a continuous outer surface 306 disposed thereabout. An associated motor (not shown) rotates the wheel 300 in a forward direction R_(F) and a reverse direction R_(R) about an axis A. Portions of the continuous outer surface 306 are described utilizing various terms, depending on their positions relative to the ground surface G and the vehicle V.

For example, a ground-engaging surface 308 of the wheel 300 is the portion of the continuous outer surface 306 that is in contact with the ground surface G. A leading surface of the wheel 300 is the portion of the continuous outer surface 306 that is facing generally in a direction of travel of the vehicle V. In FIGS. 3A and 3B, forward rotation R_(F) results in a forward direction of travel T_(F) that makes surface 310 the leading surface. Reverse rotation R_(R) results in a reverse direction of travel T_(R) that makes surface 312 the leading surface. Forward rotation R_(F) of the wheel 300 also exerts a force F_(F) from the ground-engaging surface 308 to the ground surface G, which results in the forward direction of travel T_(F). Reverse rotation R_(R) of the wheel 300 exerts a force F_(R) from the ground-engaging surface 308 to the ground surface G, which results in the reverse direction of travel T_(R). The amount of force F_(F) on F_(R) applied to the ground surface G may vary based on vehicle weight, wheel 300 rotational speed, center of gravity of the vehicle, or other factors.

With the above structures and concepts in mind, FIGS. 4A and 4B depict a top and a rear schematic views, respectively, of a vehicle 400 moving in a default direction DD (e.g., a forward straight direction). In FIGS. 4A and 4B, the components of the vehicle 400 are depicted schematically, so as to illustrate the relevant aspects of the components utilized. A vehicle body 401 is only depicted in FIG. 4B. The vehicle 400 includes a chassis 410 and two driven front wheels 402 a, 402 b connected via a linkage 411, which may be controlled by a linkage actuator 413. Individual motors 404 a, 404 b drive each of the front wheels 402 a, 402 b. Leading surfaces 406 a, 406 b of each of the front wheels 402 a, 402 b generally face in a wheel direction WD. Trailing link actuators 408 a, 408 b and trailing links 409 a, 409 b, such as those described above, are also provided proximate each wheel 402 a, 402 b. Two passive rear wheels 412 a, 412 b are connected via a live axle 414, which is connected to the chassis at a pivoting interface 415. Recesses such as wheel wells may be formed in the body 401 and/or chassis 410 to prevent contact between those elements and the wheels 402 a, 402 b, 412 a, 412 b during the various driving and turning operations described herein. Additionally, FIG. 4 depicts a center of gravity shift mechanism 416 that is fixed to the chassis 410. The shift mechanism 416 includes a lead screw 418 having a counterweight 420 movably disposed thereon. The lead screw 418 may be rotated by an actuator 422 to as to move the counterweight 420 along the lead screw 418. This shifts the center of gravity of the vehicle 400 between the front wheels 402 a, 402 b for performance purposes as described below, but is typically not utilized during movement in the default direction DD.

When moving in the default direction DD, the leading surfaces 406 a, 406 b point in a wheel direction WD generally parallel with the default direction DD. A generally equal forward rotational rate R_(F) is applied to each wheel 402 a, 402 b, by its associated motor 404 a, 404 b, keeping a datum D (e.g., a predetermined point on the chassis 410) moving along the default direction DD. This equal forward rotational rate R_(F) also may be referred to as the default rotational rate. The trailing link actuators 408 a, 408 b maintain a substantially equal position of the trailing links 409 a, 409 b relative to the chassis 410 and body 401. Thus, from the rear view depicted in FIG. 4B, the vehicle 400 appears substantially level with a ground surface G.

FIGS. 5A and 5B depict schematic top and rear views, respectively, of the vehicle 400 of FIGS. 4A and 4B performing a standard turn. Certain of the elements depicted in FIGS. 5A and 5B are described above with regard to FIGS. 4A and 4B and, as such, are not necessarily described further. Moreover, only a right hand standard turn is depicted. A person of skill in the art would understand the positioning of the various elements to perform a left standard turn. FIG. 5A also depicts the default direction DD and a curve C along which the vehicle 400 may turn. In an example, this curve C may be defined by movement of the datum D on the chassis 410 during a turn. The curve C has a center point CP, which is disposed at a radius of curvature r_(C) of the curve C. Thus, a turn of the vehicle 400 along the curve C may result in a turn having a general direction GD. In the depicted figure, the general direction GD of the turn made by the vehicle is to the right, since the general direction GD is located to the right of the default direction DD. Moreover, for the purposes of explanation, the wheel 402 a may be referred to the “inside wheel,” since it is disposed proximate the center point CP and thus on the inside of the curve C as the vehicle 400 turns. Conversely, the wheel 402 b may be referred to as the “outside wheel,” since it is disposed distal the center point CP and thus on the outside of the curve C as the vehicle 400 turns. Of course, if the vehicle was to turn in a general direction GD to the left, the wheel 402 b would be the inside wheel, while the wheel 402 a would be the outside wheel. During a standard turn, the trailing link actuators 408 a, 408 b may (but need not) maintain a substantially equal position of the trailing links 409 a, 409 b relative to the chassis 410 and body 401. Thus, from the rear view depicted in FIG. 5B, the vehicle 400 appears substantially level with a ground surface G. Moreover, during a standard turn, the center of gravity shift mechanism 416 is generally not utilized, but may be if desired.

The steps for performing a standard turn will now be described. First, it is assumed that the vehicle 400 is traveling in the default direction DD due to a forward rotation R_(F) of both wheels 402 a, 402 b. If a turn in the right general direction GD is desired, the wheels 402 a, 402 b are turned by the linkage 411 such that the leading surfaces 406 a, 406 b face in the right wheel direction WD. The wheel direction WD is not meant to match identically the general direction GD, e.g., as measured by an angular deviation from the default direction DD. Instead, if the general direction GD is to the right of the default direction DD, the wheel direction WD should also point to the right of the default direction DD. As forward rotation R_(F) of the wheels 402 a, 402 b continues, the vehicle will move in the right general direction GD as the vehicle 400 (as defined by the datum D) moves along curve C. In general, during a standard turn, the wheels 402 a, 402 b are rotated by the motors 404 a, 404 b at the same angular rotation rate. As the front wheels 402 a, 402 b pull the vehicle 400 through the curve C, the rear wheels 412 a, 412 b passively rotate and follow a curvature similar to curve C (e.g., to a vehicle 400 turned position depicted in dashed lines).

FIGS. 6A and 6B depict schematic top and rear views, respectively, of the vehicle 400 of FIGS. 4A and 4B performing a drift turn to the right. Certain of the elements depicted in FIGS. 6A and 6B are described above with regard to FIGS. 4A and 4B and, as such, are not necessarily described further. A curve C along which the vehicle 400 may turn is also depicted and, again, may be defined by a movement of the datum D during the turn. The curve C has a center point CP, which is disposed at a radius of curvature r_(C) of the curve C. Thus, a turn of the vehicle 400 along the curve C may result in a turn having a general direction GD. In the depicted figure, the general direction GD of the turn made by the vehicle is right, since the general direction GD is located to the right of the default direction DD. The wheel 402 a is the inside wheel and the wheel 402 b is the outside wheel.

The steps for performing a drift turn will now be described. First, it is assumed that the vehicle 400 is traveling in the default direction DD due to a forward rotation R_(F) of both wheels 402 a, 402 b by the motors 404 a, 404 b at a default rotational speed that is substantially the same. If a drift turn in the right general direction GD is desired, the wheels 402 a, 402 b are turned by the actuator 413 and linkage 411 such that the leading surfaces 406 a, 406 b face in the left wheel direction WD, which is generally opposite the desired direction of turn to the right. One or more operations that may be performed by the various motors or actuators (e.g., wheel motors 404 a, 404 b; trailing link actuators 408 a, 408 b; and/or center of gravity shift mechanism actuator 422) that are included on the vehicle 400 to perform the drift turn.

For example, the motors 404 a, 404 b that drive the wheels 402 a, 402 b may create a differential rotation therebetween. In one example, the outside wheel 402 b may be rotated at a forward rotational rate +R_(F) that greater than a rotational rate of the inside wheel 402 a, which may maintain the default rotational rate, described above. In another example, the inside wheel 402 a may be rotated at a forward rotational rate −R_(F) less than a rotational rate of the outside wheel 402 b, which may maintain the default rotational rate R_(F). In yet another example, a rotational direction of the inside wheel 402 a may change from the default (e.g., forward) direction to a reverse rotational direction R_(R). In another example, more than one of these actions may be initiated (e.g., the outside wheel 402 b may increase rotational rate while the inside wheel 402 a may reverse rotation). Other combinations of actions to create differential rotation between the driven wheels 402 a, 402 b are contemplated.

In another example, the actuators 408 a, 408 b, and 422 may be utilized to shift the center of gravity of the vehicle 400. In the depicted vehicle 400, this may be accomplished in at least two ways. In a first example, the shift mechanism 416 may be utilized to shift a center of gravity of the vehicle 400. The center of gravity shift mechanism actuator 422 may rotate the lead screw 418 so as to draw the counterweight 420 proximate the inside wheel 402 a. This shifts the center of gravity of the vehicle 400, enabling performance of the drift turn. In a second example, the trailing link actuator 408 b disposed proximate the outside wheel 402 b may apply a force to associated the trailing link 409 b, thus lifting the chassis 410 proximate the outside wheel 402 b, which shifts the center of gravy of the vehicle 400. FIG. 6B depicts an end view of the vehicle 400 during such a lifting operation, which results in an increased elevation of portions of the chassis 410 and body 401 located proximate the outside wheel 412 b. As can be seen, the live axle 414 connects the passive rear wheels 412 a, 412 b. Movement of the chassis 410 causes pivoting P at the interface 415, this allowing the rear wheels 412 a, 412 b to remain in contact with a ground surface G. Again, recesses such as wheel wells may be formed in the body 401 and/or chassis 410 to prevent contact between those elements and the wheels 402 a, 402 b, 412 a, 412 b during these operations. As the front wheels 402 a, 402 b pull the vehicle 400 through the curve C, the rear wheels 412 a, 412 b passively rotate. Additionally, due to the low coefficient of friction, the rear wheels 412 a, 412 b slide relative to the ground surface G in an altered curvature AC that may be dissimilar to curve C (e.g., to a vehicle 400 turned position depicted in dashed lines).

FIGS. 7A and 7B depict schematic top and rear views, respectively, of the vehicle 400 of FIGS. 4A and 4B performing a drift turn to the left. Certain of the elements depicted in FIGS. 6A and 6B are described above with regard to FIGS. 4A and 4B and, as such, are not necessarily described further. A curve C along which the vehicle 400 may turn is also depicted and, again, may be defined by a movement of the datum D during the turn. The curve C has a center point CP, which is disposed at a radius of curvature r_(C) of the curve C. Thus, a turn of the vehicle 400 along the curve C may result in a turn having a general direction GD. In the depicted figure, the general direction GD of the turn made by the vehicle is left, since the general direction GD is located to the left of the default direction DD. The wheel 402 b is the inside wheel and the wheel 402 a is the outside wheel.

The steps for performing a drift turn will now be described. First, it is assumed that the vehicle 400 is traveling in the default direction DD due to a forward rotation R_(F) of both wheels 402 a, 402 b by the motors 404 a, 404 b at a default rotational speed that is substantially the same. If a drift turn in the left general direction GD is desired, the wheels 402 a, 402 b are turned by the actuator 413 and linkage 411 such that the leading surfaces 406 a, 406 b face in the right wheel direction WD, which is generally opposite the desired direction of turn to the left. One or more operations that may be performed by the various motors or actuators (e.g., wheel motors 404 a, 404 b; trailing link actuators 408 a, 408 b; and/or center of gravity shift mechanism actuator 422) that are included on the vehicle 400 to perform the drift turn.

As described above, the motors 404 a, 404 b that drive the wheels 402 a, 402 b may create a differential rotation therebetween. In one example, the outside wheel 402 a may be rotated at a forward rotational rate +R_(F) that greater than a rotational rate of the inside wheel 402 b, which may maintain the default rotational rate, described above. In another example, the inside wheel 402 b may be rotated at a forward rotational rate −R_(F) less than a rotational rate of the outside wheel 402 a, which may maintain the default rotational rate R_(F). In yet another example, a rotational direction of the inside wheel 402 b may change from the default (e.g., forward) direction to a reverse rotational direction R_(R). In another example, more than one of these actions may be initiated (e.g., the outside wheel 402 a may increase rotational rate while the inside wheel 402 b may reverse rotation). Other combinations of actions to create differential rotation between the driven wheels 402 a, 402 b are contemplated.

In another example, the actuators 408 a, 408 b, and 422 may be utilized to shift the center of gravity of the vehicle 400. In the depicted vehicle 400, this may be accomplished in at least two ways. In a first example, the shift mechanism 416 may be utilized to shift a center of gravity of the vehicle 400. The center of gravity shift mechanism actuator 422 may rotate the lead screw 418 so as to draw the counterweight 420 proximate the inside wheel 402 b. This shifts the center of gravity of the vehicle 400, enabling performance of the drift turn. In a second example, the trailing link actuator 408 a disposed proximate the outside wheel 402 a may apply a force to associated the trailing link 409 a, thus lifting the chassis 410 proximate the outside wheel 402 a, which shifts the center of gravy of the vehicle 400. FIG. 6B depicts an end view of the vehicle 400 during such a lifting operation, which results in an increased elevation of portions of the chassis 410 and body 401 located proximate the outside wheel 412 a. As can be seen, the live axle 414 connects the passive rear wheels 412 a, 412 b. Movement of the chassis 410 causes pivoting P at the interface 415, this allowing the rear wheels 412 a, 412 b to remain in contact with a ground surface G. Recesses such as wheel wells may be formed in the body 401 and/or chassis 410 to prevent contact between those elements and the wheels 402 a, 402 b, 412 a, 412 b during these operations. As the front wheels 402 a, 402 b pull the vehicle 400 through the curve C, the rear wheels 412 a, 412 b passively rotate. Additionally, due to the low coefficient of friction, the rear wheels 412 a, 412 b slide relative to the ground surface G in an altered curvature AC that may be dissimilar to curve C (e.g., to a vehicle 400 turned position depicted in dashed lines).

The above described changes in wheel rotational rates, changes in wheel rotational directions, or shifts in vehicle center of gravity may be used in any combination to cause drift turns of a toy vehicle. For example, rotation of the outside wheel may be increased while also shifting a center of gravity by raising the chassis proximate thereto so as to drift turn the vehicle. This causes a drift turn, as well as alters a visual impression of the vehicle during the turn to mimic such a drift turn of large-scale vehicles. This can be entertaining for the user/operator of the toy. Additionally, while drift turns on large-scale vehicles such as sports cars are typically performed at fairly high speeds, the structures and functionality of the present technology can generate drift turns for toy vehicles at speeds of less than 10 miles/hour. For example, at eight miles/hour, six miles/hour, four miles/hour, and two miles/hour.

FIG. 8 depicts a method 500 of moving a vehicle, such as the vehicles depicted in the above figures. The method 500 may be utilized to move the vehicle in a general direction of a curve, where the curve may be defined by a center point and a radius of curvature. The method contemplates movements such as drift turns. The method begins by moving a vehicle in a default direction, operation 502 a, typically by applying a first force from one driven wheel of the vehicle to a ground surface, operation 502 b. As described above, this first force is caused by a rotation of a driven wheel against the ground surface. Flow continues to operation 504, where a leading surface of the driven wheel is turned in a direction away from the general direction of the curve. More specifically, if the desired curve turns to the right, the leading surface is turned to the left; if the desired curve turns to the left, the leading surface is turned to the right. In operation 506, a second force is applied from the wheel to the ground surface, which moves the vehicle in the direction of the curve.

A number of different operations to apply the second force are contemplated and are depicted in FIG. 8. For example, a difference in rotational speeds may be introduced to driven wheels in a vehicle having a plurality of such driven wheels. For example, operation 506 a contemplates accelerating a rotational speed of one of the driven wheels. In a vehicle that has a plurality of driven wheels, the accelerated wheel is distal to a center point of the curve and may be called the outside wheel. Operation 506 b contemplates decelerating a rotational speed of one of the driven wheels; for example, an inside wheel located proximate the center point. Operation 506 c describes reversing a direction of rotation of the wheel, which would be the inside wheel. Any of operations 506 a-506 c change the force applied by at least one wheel against the ground surface, so as to turn the vehicle as desired.

Other operations to apply the second force are depicted in FIG. 8. Operation 506 d contemplates changing a center of gravity of the vehicle. This may be accomplished by shifting a distribution of weight within the vehicle, for example, by moving a movable counterweight disposed in or on the vehicle. Operation 506 d′ describes an enhanced operation, where a portion of the vehicle is elevated, for example, by the trailing arm actuators, discussed above. In both operations 506 d and 506 d′, the center of gravity of the vehicle is shifted so as to be closer to the inside wheel, thus enabling the drift turn.

FIG. 9 depicts a method 600 of controlling a vehicle, such as the vehicles depicted in the above figures. The method 600 contemplates controlling the vehicle so as to initiate drift turns and begins with sending a default control signal to a control module of a vehicle, operation 602. The control module controls at least one of a rotational speed of a driven wheel, a rotational direction of a driven wheel, a weight distribution within the vehicle, and an elevation of a portion of the vehicle. The default signal sent thereto initiates default operation of various components, for example to move the vehicle straight forward at a default rate of speed. In operation 604, a desired direction signal is received from a vehicle driving controller. The desired direction signal may correspond to a desired direction of turn of a vehicle and may be initiated by a remote operator of the vehicle direction controller or by a control program for the vehicle. Based on this desired direction signal, a linkage direction signal is sent to the control module. The linkage direction signal is configured to change a directional position of the wheel (or of multiple wheels where multiple driven wheels are utilized). This changed position is in a direction generally opposite the desired direction of turn identified above. That is, if the desired direction is to the right, the directional position of the wheel is turned to the left (based on the position of a leading surface of the wheel); if the desired direction is to the left, the leading surface is turned to the right. In operation 606, a command signal is sent to the control module so as to turn the vehicle in the desired direction.

A number of different command signals are contemplated. For example, the command signal may increase a rotational speed of the driven wheel to a command signal speed greater than a default speed associated with the default signal. In a vehicle that has a plurality of driven wheels, the accelerated wheel is distal to a center point of the curve and may be called the outside wheel. In another example, the command signal may decrease a rotational speed of the driven wheels to a command signal speed less than a default speed associated with the default signal. This decrease in rotational speed may be applied to an inside wheel located proximate the center point. In yet another example, the command signal may reverse a direction of rotation of the wheel to be opposite the default rotation associated with the default signal. In another example, multiple command signals may be sent. Other command signals may change a center of gravity of the vehicle to be different than the default center of gravity associated with the default signal. In another example, an elevation of a portion of the vehicle may be changed to a command signal elevation that is different than a default elevation associated with the default signal.

This disclosure described some examples of the present technology with reference to the accompanying drawings, in which only some of the possible examples were shown. Other aspects can, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein. Rather, these examples were provided so that this disclosure was thorough and complete and fully conveyed the scope of the possible examples to those skilled in the art.

Although specific examples were described herein, the scope of the technology is not limited to those specific examples. One skilled in the art will recognize other examples or improvements that are within the scope of the present technology. Therefore, the specific structure, acts, or media are disclosed only as illustrative examples. Examples according to the technology may also combine elements or components of those that are disclosed in general but not expressly exemplified in combination, unless otherwise stated herein. The scope of the technology is defined by the following claims and any equivalents therein. 

What is claimed is:
 1. An apparatus comprising: a chassis; a pair of rear wheels passively rotatably coupled to the chassis; a pair of front wheel sets, wherein each pair of front wheel sets comprises: an upright; a motor fixed to the upright; and a front wheel fixed relative to the upright and engaged with the motor; a linkage coupling the chassis to each of the uprights of the pair of front wheel sets, wherein the linkage is configured to move the uprights in a first range of motion; and a linkage actuator for actuating the linkage.
 2. The apparatus of claim 1, further comprising a controller fixed to the chassis for sending control signals to the motors and the linkage actuator.
 3. The apparatus of claim 2, further comprising a pair of trailing link actuators, and wherein each front wheel set comprises a trailing link connecting the upright to one of the pair of trailing link actuators.
 4. The apparatus of claim 3, wherein the trailing link is configured to allow movement of the upright in a second range of motion different than the first range of motion.
 5. The apparatus of claim 4, wherein the first range of motion and the second range of motion are substantially orthogonal.
 6. The apparatus of claim 1, wherein the linkage includes Ackermann steering geometry.
 7. The apparatus of claim 2, wherein the controller is configured to send a motor signal to at least one of the motors so as to at least one of (1) rotate the front wheels at different rotational speeds, and (2) rotate the front wheels in different rotational directions.
 8. The apparatus of claim 3, wherein the controller is configured to send an actuator signal to at least one of the trailing link actuators so as to actuate at least one of the trailing links.
 9. The apparatus of claim 1, wherein each of the pair of rear wheels comprise a coefficient of friction less than a coefficient of friction of each of the pair of front wheels.
 10. The apparatus of claim 1, wherein the pair of rear wheels are coupled to by an axle that is configured to pivot relative to the chassis.
 11. A method of moving a vehicle along a ground surface in a general direction of a curve, wherein the curve comprises a curve radius and a center point, and wherein the vehicle comprises a plurality of driven front wheels and a plurality of passive rear wheels, and wherein the plurality of driven front wheels comprise an inside front wheel disposed proximate to the center point and an outside front wheel disposed distal from the center point, the method comprising: moving the vehicle in a default direction of travel by applying a first force from a ground-engaging surface of at least one of the plurality of driven front wheels to the ground surface; turning a leading surface of the plurality of driven front wheels in a wheel direction away from a general direction of the curve; and applying a second force from the ground-engaging surface of at least one of the plurality of driven front wheels to the ground surface, so as to move the vehicle in the general direction of the curve.
 12. The method of claim 11, wherein applying the second force comprises accelerating a rotational speed of the outside wheel to an accelerated rotational speed greater than a default rotational speed applied to the outside wheel during the default moving operation.
 13. The method of claim 11, wherein applying the second force comprises decelerating a rotational speed of the inside wheel to a decelerated rotational speed less than a default rotational speed applied to the inside wheel during the default moving operation.
 14. The method of claim 11, wherein applying the second force comprises reversing a direction of rotation of the inside wheel to a reversed rotational direction opposite a default rotational direction applied to the inside wheel during the default moving operation.
 15. The method of claim 11, wherein applying the second force comprises changing a center of gravity of the vehicle.
 16. The method of claim 15, wherein changing the center of gravity of the vehicle comprises elevating at least a portion of the vehicle proximate the outside wheel to a raised elevation higher than a default elevation of the portion of the vehicle during the default moving operation.
 17. A method of controlling a vehicle, the method comprising: sending a default signal to a vehicle control module, wherein the vehicle control module controls at least one of a rotational speed of a wheel, a rotational direction of the wheel, a center of gravity of the vehicle, and an elevation of a portion of the vehicle; receiving a desired direction signal from a vehicle driving controller, wherein the desired direction signal is associated with a desired direction of a turn of the vehicle; based at least in part on the desired direction signal, sending a linkage direction signal to the control module so as to change a directional position of the wheel, wherein the changed directional position of the wheel is in a direction generally opposite the desired direction of the turn of the vehicle; and based at least in part on the desired direction signal, sending a command signal to the control module so as to turn the vehicle generally in the desired direction.
 18. The method of claim 17, wherein the command signal increases the rotational speed of the wheel to a command signal speed greater than a default speed associated with the default signal.
 19. The method of claim 17, wherein the command signal decreases the rotational speed of the wheel to a command signal speed less than a default speed associated with the default signal.
 20. The method of claim 17, wherein the command signal reverses the rotational direction of the wheel to a command signal rotational direction opposite a default rotation associated with the default signal.
 21. The method of claim 17, wherein the command signal changes a center of gravity of the vehicle to a command signal center of gravity different than a default center of gravity associated with the default signal.
 22. The method of claim 17, wherein the command signal changes the elevation of the portion of the vehicle to a command signal elevation different than a default elevation associated with the default signal. 